Multicast: A multicast address is associated with a group of interested receivers. According to RFC 3171, addresses 224.0.0.0 to 239.255.255.255, the former Class D addresses, are designated as multicast addresses in IPv4. The sender sends a single datagram (from the sender's unicast address) to the multicast address, and the intermediary routers take care of making copies and sending them to all receivers that have registered their interest in data from that sender.

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You don't need to be a genius to debug a pf.conf firewall ruleset, you just need the guts to run tcpdump

Thanks for the reply. Call me an idiot, but I still don't seem to fully get it. I can see there addresses different to multicasts, so still dont know how could they be sent from inside my network. Besides how is it possible that this IANA can send from inside my network anyway ?!

Hosts connected to the switch are my desktop and my two laptops. Hosts connected to the AP are 2 more laptops and my mobile phone (which has wifi normally switched off and I'm sure this problem appeared when I didn't even have it on the network yet).

After a lot of tests I figured out what causes those wierd logs. It's one of the laptops at my network running Skype v4.2. I also use older version of skype on different machine and don't seem to generate that crap, so there must be something about that newish soft.